Analytical threshold voltage model for ultrathin SOI MOSFET's including short-channel and floating-body effects

Short-channel effects (SCE) in ultrathin silicon-on-insulator (SOI) fully depicted (FD) MOSFET's are analyzed and an analytical model for threshold voltage, including the kink effect, is presented. The proposed model accounts for 1) a general nonuniform channel doping profile, 2) the drain-induced V-th-lowering enhancement resulting from the interaction of (a) impact ionization, (b) floating-body, and (c) parasitic-bipolar effects. Good agreement between the proposed model and experimental data is demonstrated. Impact ionization and floating-body effects dominate V-th lowering for drain voltages larger than V-dk similar or equal to B-i . lambda(i)/3, where B-i is the impact ionization coefficient, and lambda(i) is the impact ionization length, a structural parameter which, for a single-drain SOI MOSFET, coincides with the SCE characteristic length lambda.